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Pflugers Arch. 1989 Dec;415(3):355-60.

The effect of long-term administration of alpha 1-blocker prazosin on capillary density in cardiac and skeletal muscle.

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Department of Physiology, University of Birmingham, UK.


The effect of prazosin on heart and muscle blood flow and capillary density was studied in rats. In acute experiments, alpha 1-blocker prazosin almost trebled blood flow in fast skeletal muscles [tibialis anterior (TA) and extensor digitorum longus (EDL)], but did not affect coronary flow when infused i.v. at a dose of 0.5 for 30 min. Prazosin in an equivalent dose was then given orally over a period of 5 weeks to investigate its effect on capillarisation in heart and skeletal muscle. Capillary density (CD,, estimated in frozen sections stained for alkaline phosphatase, was similar in the hearts of prazosin-treated and control rats. Capillary/fibre ratio in skeletal muscles increased from 1.52 +/- 0.019 in control EDL to 1.69 +/- 0.01 (P less than 0.001) and from 1.56 +/- 0.04 in control TA to 2.16 +/- 0.04 (P less than 0.001). In TA, the increase was greater than in EDL both in the glycolytic periphery (from 1.30 +/- 0.13 to 1.75 +/- 0.11, P less than 0.025) and the oxidative core of the muscle (from 1.837 +/- 0.14 to 2.51 +/- 0.12, P less than 0.005). Unilateral crush of the lateral peroneal nerve and subsequent reinnervation over the next 7 weeks resulted in redistribution of fibre types from a typical mosaic pattern into groups composed of fibres of similar oxidative capacity. Capillary density as well as capillary/fibre ratio in purely glycolytic areas was lower when compared to supply of glycolytic fibres in normal muscles.(ABSTRACT TRUNCATED AT 250 WORDS).

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